Chapter 2: Flexible Properties: Adsorptive Storage and Separation

When compared to conventional porous materials, metal–organic frameworks can show much larger flexibility in responses to the change of external chemical (guest) and physical (temperature, pressure, light, etc.) environments, giving rise to unique and controllable adsorption behaviours that are potentially useful for improving the performances of related applications. However, there are still many controversial understandings about the roles of various types of flexibility for adsorptive storage and separation. This chapter analyses the thermodynamic and kinetic mechanisms of flexibility/dynamism under chemical and physical stimuli. Based on representative examples, the role of typical types of flexibility (pore-opening/pore-closing and gating behaviours) for adsorptive storage and separation is discussed, focusing on critical performances such as working capacity, selectivity, co-adsorption and purity.